Earlier quoted context omitted.
This reads like you're suggesting to not even try. IME trying new things is a great way to learn. Also, if a dev can close a few sales, just the first few, then they'll know how to help their sales staff. Try a little, see if you can grow.
I wish people didn’t have such a knee jerk reaction to my advice, but for many years I too believed a dev should at least try to wear many hats. All it took was seeing how professionals always do the job far better to change my mind. It doesn’t matter if a dev picks up some skills, if you plan to be a dev then a dev is all you’ll ever be, focus on the development and let sales worry about sales. I see a lot of founde…
I get that once a business grows to a certain point it needs "professionals" to do some of the tasks. Ideally start by hiring people with skills you don't have. Sales is a skill.
That said many people have more the one skill. Context matters. I write libraries for programmers. I attend trade events where I talk to, and sell to programmers. I do a lot of marketing in this space. I have an authenticity that a non-programmer does not have, and I believe that is reflected in our sales.
In this case the developer is perfectly capable of picking up the phone. They may or may not maximise potential income (but that's not their stated goal). If there's enough demand then they can pivot to a sales person later on.
Incidentally, I would likely figure out who does the marketing for the local businesses you see. They buy the ads, not the business directly. They're easier to talk to (they -want- more exposure opportunities) and they may bring multiple customers to the table.